1. Field of the Invention
The present invention generally relates to an optical device, and more particularly, to a lens structure.
2. Description of Related Art
Along with the progress of modern video technology, image apparatuses, such as digital video recorder (DV) and digital camera (DC), have been broadly used by people today. One of the kernel components in the image apparatuses is zoom lens, by adjusting which a sharp image can be focused on a charge coupled device (CCD) for imaging. Obviously, the optical quality of the zoom lens is closely bound of the image quality.
A common zoom lens includes a front cell and a rear cell, wherein the front cell usually is for focusing and the rear cell is for zooming. When the lens is zooming and focusing, driving devices are used to drive the front cell and the rear cell. That is, the front cell is in charge of adjusting focal length to make an image sharp; the rear cell is in charge of adjusting magnification to zoom in or zoom out the image; and operations of the front cell and the rear cell are independent. Specially, when the rear cell reaches a preset position by manually adjusting or using a drive motor or a gear transmission module, the front cell then reaches another preset position by manually adjusting or using another drive motor or another gear transmission module. In this way, the magnification adjustment and the focusing are implemented.
Note that since a conventional zoom lens requires different driving devices for zooming and focusing, therefore, it takes more time to adjust a conventional front cell and a rear cell to correct positions, which leads to a poor focusing efficiency. Besides, the required two sets of driving devices for driving the front cell and the rear cell bring a higher product cost with a conventional zoom lens.